I have an 8T5 chassie I use as an engine test stand for ET engines. It was originally an early style blue hood ET300 with a green stripe in the decals. I think it is an 82 chassie maby 81. So the 8T6 could be an 82 ET340??? Call your dealer he should be able to tell you right away if he is any good.
Good Luck, Phil (opsled)